By coupling black phosphorus (BP) nanoplatelets (NPs) with a fiber-taper evanescent light field, a saturable absorber (SA) based on the BP NPs has been successfully fabricated and used in a thulium/holmium-doped fiber laser as the mode locker. The SA had a modulation depth of ∼9.8% measured at 1.93 μm. A stable mode-locking operation at 1898 nm was achieved with a pulse width of 1.58 ps and a fundamental mode-lock repetition rate of 19.2 MHz. By increasing the pump intensity, phenomena of multi-pulsing operations, including harmonic mode-locked states and soliton bunches, were obtained in the experiment, showing that the BP NPs possess an ultrafast optical response time. This work suggests that the BP NPs-based SA is potentially useful for ultrashort, pulsed laser operations in the eye-safe region of 2 μm.

With a serious food safety situation in China, lots of major food recalls have been initiated. This study examined the key determinants underlying consumers’ protection and behavioral intention in response to major food recalls. An augmented protection motivation theory model (PMT) was developed by incorporating trust in food safety management and food recall concern into the original PMT. Structural equation model analysis was conducted using survey data in China (N = 631). The results showed that perceived knowledge significantly and positively influence protection motivation via its positive influence on the threat appraisal and coping appraisal. Moreover, protection motivation, trust in food safety management (TFSM), and food recall concern (FRC) significantly affect protection behavior intention. It was indicated that the inclusion of TFSM and FRC into the PMT significantly increase the explanatory power of the PMT model. Further analysis of quadratic regression demonstrated that the relationship between perceived knowledge and protection motivation presented an inverted U shape, which indicates the importance of continuous education in developing consumers’ food safety knowledge. Implications for future research are discussed.

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A passively modelocked thulium/holmiumdoped fiber laser (THDFL) based on tungsten disulfide (WS 2 ) saturable absorber (SA) was demonstrated. The WS 2 nanosheets were prepared by liquid phase exfoliation method and the SA was fabricated by depositing the fewlayer WS 2 nanosheets on the surface of a fiber taper. The modulation depth, saturable intensity, and nonsaturable loss of this SA were measured to be 8.2%, 0.82 GW cm −2 , and 29.4%, respectively. Based on this SA, a stable modelocked laser operated at 1.91 µm was achieved with pulse duration of 825 fs and repetition rate of 15.49 MHz, and signaltonoise ratio (SNR) of 67 dB. Meanwhile, by increasing the pump power and adjusting the position of polarization controller, harmonic modelocking operations were obtained. These results showed that the WS 2 nanosheetbased SA could be served as a desirable candidate for a short pulse mode locker at 2 µm wavelength.

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Materials based on group IV chalcogenides exhibit extensive technologically important properties. Its unusual chemical bonding and off-centering of in-layer sublattices could cause chemical polarity and weakly broken symmetry, making optical field controlling feasible. Here, we fabricated large-area SnS multilayer films and observed unexpected strong SHG response at 1030 nm. The appreciable SHG intensities were obtained with an independence on layer, which is opposite to the generation principle of overall nonzero dipole moment only in odd-layer material. Taking GaAs for reference, the second-order susceptibility was estimated to be 7.25 pm/V enhanced by mixed-chemical bonding polarity. Further polarization-dependent SHG intensity confirmed the crystalline orientation of SnS films. The results imply surface inversion symmetry broken and nonzero polarization field modified by metavalent bonding should be the origin of SHG responses. Our observations establish multilayer SnS as a promising nonlinear material, and will guide in design of IV chalcogenides with improved optics and photonics properties for the potential applications.

For example, ultrathin flexible electrode arrays could be installed on epidermis [16] or organ surfaces [17] for real-time monitoring of human health that cannot be realized by traditional rigid electronic devices. Thus, new functional materials of flexible electronics that not only meet the demand of high performance but also have good stability and durability under reiterative bending, folding, or stretching are urgently pursued.2D transition metal dichalcogenides (2D TMDs) are a rising star in the family of 2D layered materials since their outstanding electrical and optical properties, such like tunable bandgaps, [18] high absorbance, [19] quick carrier generation, and migration. [20] More importantly, 2D TMDs materials are featured by strong covalent intralayer bonds and weak van der Waals (vdW) interlayer bonding, which make them a promising candidate to build atomicscale or nanoscale Lego devices as well as flexible electronics applications. [21][22][23] Studies have shown that covalent bond can tolerate enormously higher strains (up to 40%) than ionic bonded bulk forms (≈18%), which can enable 2D TMDs sustain the deformation over 10% before rupture, [24] while the fracture value of typical bulk semiconductors is usually less than 1%. [25] Besides, according to the dependence of the stiffness (k) on cross-section (A) and length (L) expressed as k = E × A/L, 2D TMDs are expected to have excellent flexibility with a very low k due to their ultrathin thicknesses. [26] Layered molybdenum disulfide (MoS 2 ), as a semiconductor material with an indirect bandgap of 1.2-1.8 eV (direct bandgap in monolayer materials), has been employed in lots of photoelectronic devices. Up to now, substantial developments and progresses concerned have been witnessed, especially on flexible photodetectors owing to its terrific mechanical flexibility with 11% stretch. [27] Its reducible atomic thickness greatly facilitates the design and construct for bending, crimping, and folding, whereas it comes at the expense of excellent optoelectronic properties. [28] The carrier mobilities of MoS 2 on flexible substrates range from 4.7 to 45 cm 2 V −1 s −1 , [29] while that on Si substrate is up to 480 cm 2 V −1 s −1 . [30] The high variation should be caused by introducing impurities and creating sources of extrinsic scattering in physical contacts, which reduces the mean-free path of the carriers. [31] The latest researches show that, the synergetic integration of two layered materials is a promising strategy to overcome the shortages of individual Flexible electronics is one of the hotspots of interdisciplinary research and can promote disruptive technology for post-Moore applications in the field of biomedical, electronic skin, wearable devices, etc. 2D materials have triggered great interest in flexible electronic devices since they have tunable bandgaps, excellent mechanical flexibility, good chemical stability, and outstanding optical properties. Their reducible atomic thickness greatly facilitates the design and construct for bending,...

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